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Journal ArticleDOI

3-5 compound photocathodes: A new family of photoemitters with greatly improved performance

01 Nov 1970-Vol. 58, Iss: 11, pp 1788-1802
TL;DR: In this paper, the physical principles of operation, preparation, and activation of 3-5 compound semiconductor photocathodes are discussed, as well as current fabrication techniques, problem areas, practical difficulties, and operating characteristics of experimental cathodes.
Abstract: Recently developed 3-5 compound semiconductor photocathodes show promise of substantial advantages over conventional photocathodes in increased yield and longer wavelength response. This paper reviews the physical principles of operation, preparation, and activation of these new types of photocathode. Also discussed are current fabrication techniques, problem areas, practical difficulties, and operating characteristics of experimental cathodes.
Citations
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Journal ArticleDOI
W. E. Spicer1
TL;DR: Negative electron affinity (NEA) photocathodes are defined by the relationship between the potential barrier at the surface and the bottom of the conduction band in the bulk of the material as discussed by the authors.
Abstract: Negative electron affinity (NEA) photocathodes are defined by the relationship between the potential barrier at the surface and the bottom of the conduction band in the bulk of the material. If the bottom of the conduction band liesabove the potential barrier at the surface, the device is said to have a negative electron affinity. In practice this condition is obtained by heavyp-doping of the semiconductor (to encourage downward band bending at the surface) and by adding a thin film (several atomic layers) of cesium richcesium oxide on the clean semiconductor surface. The physics, development, fabrication, and applications of the NEA cathode are reviewed.

174 citations

Journal ArticleDOI
TL;DR: In this paper, the surface escape probability of Ga1−xInxAs alloys in the composition range 0≤x≥0.52 and band gap (Eg) range of 1.38 to 0.74 eV were investigated with Cs and O2.
Abstract: Ga1−xInxAs alloys in the composition range 0≤x≥0.52 and band‐gap (Eg) range of 1.38 to 0.74 eV were activated with Cs and O2. Samples of different carrier concentrations were investigated. For band gaps down to about 0.8 eV, the photothreshold was equal to the band gap. The longest wavelength threshold determined was 1.58 μm. To the best of our knowledge, this represents the longest wavelength response yet achieved for photoemission into vacuum from a III‐V compound. The surface escape probability, B, was derived from the quantum yield data for each sample. The B‐vs‐Eg data were analyzed according to a surface escape model which includes the effects of (i) a finite‐width initial energy distribution of photoexcited carriers, (ii) the bent‐band region and (iii) various types of surface potential barriers. Surface escape probability data pertaining to a single doping density could be explained by a model that includes only a work‐function barrier or simple step potential. However, in order to explain the dat...

146 citations

Journal ArticleDOI
TL;DR: In this article, the spectrum of spin polarization and yield of photoelectrons from negative electron affinity GaAs were measured and the results show that GaAs is an excellent source of polarized electrons with P∼50%, high current, small energy spread, and high brightness.
Abstract: The spectrum of spin polarization and yield of photoelectrons from negative electron affinity GaAs were measured. The results show that GaAs is an excellent source of polarized electrons with P∼50%, high current, small energy spread, and high brightness.

102 citations

Journal ArticleDOI
TL;DR: In this article, the surface states on the cleavage GaAs (110) were analyzed using the bond orbital model and the empty and filled bands were associated with Ga and As, respectively.
Abstract: Careful photoemission studies of surface states on the cleavage GaAs (110) detect no filled states in the band gap. However, empty states pin the surface Fermi level on n ‐type GaAs at midband gap. Filled states are placed below the valence‐band maximum and empty surface states in the upper half of the band gap. Calculations, using the bond orbital model, agree with these results and associate the empty and filled bands with Ga and As, respectively.

101 citations

Journal ArticleDOI
TL;DR: In this article, a large-area field-emission photocathode is described, which consists of a finely spaced array of point emitters fabricated by etching of p-type silicon or other semiconductor.
Abstract: The recently developed large-area field-emission photocathode is described. It consists of a finely spaced array of point emitters fabricated by etching of p-type silicon or other semiconductor. Uniform emission over areas of 6-7 cm2have been obtained. For Si, the spectral response extends from 0.4 to 1.1 µm. Quantum yields of 25 percent at 0.86 µm have been measured, which is about five times the value reported for the extended S-20 photocathode and comparable to the best III-V photoemitters. Calculations indicate that quantum yields of up to 40 percent at 0.86 µm and 28 percent at 0.9 µm are attainable with the present photocathode structures. For low dark current densities, photocathode cooling to temperatures approaching 77 K must be employed at present. The dark current is shown to be dominated by surface-generated electrons in the space-chargeregion of the emitters. Effects of phosphorus gettering and annealing treatments on dark current are discussed, and the spatial frequency response of the device is determined. The results of a computer study show that the field intensification factor of p-semiconductor field emitters behaves quite differently from that of metallic emitters.

75 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the authors derived a model for the photoemission from these materials which fits the three last materials listed above in addition to the surface layers of Cs or Rb added.
Abstract: By means of absorption and photoconductivity measurements, the following band gaps were found: ${\mathrm{Na}}_{3}$Sb---1.1 ev; ${\mathrm{K}}_{3}$Sb---1.1 ev; ${\mathrm{Rb}}_{3}$Sb---1.0 ev; ${\mathrm{Cs}}_{3}$Sb---1.6 ev; and ${(\mathrm{NaK})}_{3}$Sb---1.0 ev. A model has been derived for the photoemission from these materials which fits the three last materials listed above in addition to the ${(\mathrm{NaK})}_{3}$Sb with surface layers of Cs or Rb added. The electron affinities found from the photoemissive data using this model were as follows: ${\mathrm{Rb}}_{3}$Sb---1.2 ev; ${\mathrm{Cs}}_{3}$Sb---0.45 ev; ${(\mathrm{NaK})}_{3}$Sb---1.0 ev; [Rb]${(\mathrm{NaK})}_{3}$Sb---0.70 ev; and [Cs]${(\mathrm{NaK})}_{3}$Sb---0.55 ev. The electron affinity of ${\mathrm{K}}_{3}$Sb was estimated to be between 1.1 and 1.8 ev and that of ${\mathrm{Na}}_{3}$Sb to be between 2.0 and 2.4 ev. By means of the temperature dependence of the photoemission, ${\mathrm{Rb}}_{3}$Sb, ${\mathrm{Cs}}_{3}$Sb, and the multi-alkali materials were found to have $p$-type conductivity; whereas ${\mathrm{K}}_{3}$Sb and ${\mathrm{Na}}_{3}$Sb were found to have $n$-type conductivity.

435 citations

Journal ArticleDOI
TL;DR: A semi-empirical approach for predicting the type of contact to be expected at an arbitrary metal-semiconductor interface is presented in this paper, where the physical principles underlying the metal-semiconductor barrier are discussed in the light of recent experimental results.
Abstract: The physical principles underlying the metal-semiconductor barrier are discussed in the light of recent experimental results. A semi-empirical approach for predicting the type of contact to be expected at an arbitrary metal-semiconductor interface is presented.

400 citations

Journal ArticleDOI
TL;DR: In this article, the decomposition of alkyl-gallium compounds in the presence of arsine, phosphine, arsinesinephosphine, and stibine mixtures has been used for compound semiconductor film growth compatible with methods used for the growth of elemental semiconductors.
Abstract: Single‐crystal , , and films have been grown on and a number of insulating substrates by the decomposition of alkyl‐gallium compounds in the presence of arsine, phosphine, arsine‐phosphine, and arsine‐stibine mixtures. Both triethylgallium and trimethylgallium have been used successfully in the preparation of . This process makes compound semiconductor film growth compatible with methods used for the growth of elemental semiconductors and eliminates many of the difficulties inherent in multitemperature‐zone processes.

313 citations

Journal ArticleDOI
J.J. Scheer1, J. van Laar1
TL;DR: In this paper, the p-type GaAs-Cs should have very good properties as a photoemitter, and this was verified by experiments on vacuum cleaved single crystals.

215 citations